The Brazil midfielder, who was linked with Juventus during the summer, has committed his future to the Blues, who are enduring a challenging season in defence of their Premier League title
Chelsea announced the deal on Thursday evening.
Mourinho, who in August signed a four-year contract committing himself to Stamford Bridge until June 2019, was subject to the first vote of confidence of Roman Abramovich's 12-year ownership on October 5.
Since then, Chelsea have won one of their four matches - against a free-falling Aston Villa; the latest defeat was on penalties to Stoke in Tuesday night's Capital One Cup tie - while Mourinho has faced disciplinary action from the Football Association.
The 52-year-old Portuguese had until 1800 on Thursday to respond to a misconduct charge following his half-time touchline dismissal at West Ham last Saturday.
Mourinho is already appealing a separate Â£50,000 fine and suspended one-match stadium ban for comments made after the October 3 loss to Southampton, a result which prompted the vote of confidence.
It is not expected either case will be heard before Saturday's match with Jurgen Klopp's Liverpool.
Source : PA